A roof shell of this kind is known from practice and can be a fixed roof of a motor vehicle or a roof segment of a retractable hard top of a convertible vehicle, the retractable hard top comprising multiple rigid roof segments. The roof shell can also be realized as what is known as a composite module which comprises a panel-type rigid composite component which is provided with an additional acoustic insulation layer at its inner side. The composite component can be of a sandwich design and comprise a core layer which is formed by a paper honeycomb or a foam material, for example, and which is provided with a glass-fiber/polyurethane mixture on both sides. Moreover, the composite component can comprise an outer skin of the vehicle roof in question, the outer skin thus matching the design of the vehicle in question. The acoustic insulation layer serves to acoustically insulate the vehicle interior from the surroundings of the vehicle. However, acoustic insulation layers used so far present the problem that seams between the acoustic insulation layer and the composite component as well as irregularities on the inner side of the composite component may become apparent on the acoustic insulation layer at the inner side of the roof shell, in particular at a headliner fabric applied thereto as a lining.
The object of the invention is to provide a roof shell of the kind mentioned above that has an optimized acoustic insulation layer.
According to the invention, this object is attained by the roof shell having the features of claim 1.
Thus, a roof shell of a motor vehicle is proposed that comprises a panel-type rigid composite component having an outer side and an inner side, which faces a vehicle interior. Moreover, the roof shell comprises an acoustic insulation layer disposed on the inner side of the composite component. The composite component has at least one tray-like recess on its inner side, said recess being filled with an open-pored foam material which forms the acoustic insulation layer and whose surface is flush with the surface of the composite component surrounding the recess.
With the roof shell designed according to the invention, the edges of the composite component thus remain free of the acoustic insulation layer. The acoustic insulation layer thus does not reach the edges of the rigid composite component. This ensures that the inner side of the roof shell can be lined and the lining can have an edge fold at its edges that wraps around the edges of the composite component. Additionally, it should be made sure that the open-pored foam material that fills the tray-like recess does not shrink during setting so that there will be no height difference or gap between the surface of the composite component surrounding the recess and the foam material filling the tray-like recess. This ensures that the inner side of the roof shell can be lined properly.
In a preferred embodiment of the roof shell according to the invention, the open-pored foam material is a fine-pored flexible foam. In particular, the fine-pored flexible foam can be a polyurethane foam having a density between 50 kg/m3 and 80 kg/m3.
Preferably, the foam material is introduced into the tray-shaped recess according to a foaming process in a foaming mold. A foaming process of this kind can be performed in short process times, i.e. at a high cycle rate. Moreover, the mold-based process in the foaming mold allows achieving high process stability, which, in turn, has a positive effect on the expenditures required for quality control.
In the foaming process in the foaming mold, an external release agent acting as a pore opener is preferably used. This has a favorable effect on the acoustic insulation properties of the foam material.
The bottom of the tray-like recess can present irregularities or protrusions or can be rippled. This may be caused by functional elements integrated in the composite component. The foam material forming the acoustic insulation layer accommodates these irregularities, i.e. encloses them, while being smooth and even, i.e. free of protrusions or steps, at its surface. In this way, the system is independent of any influences that may be caused by changes in geometry of the composite component.
The invention also relates to a roof shell of a motor vehicle that comprises a panel-type rigid composite component having an outer side and an inner side, which faces the vehicle interior. An acoustic insulation layer disposed on the inner side of the composite component is formed by at least one rigid-foam or semi-rigid-foam plate which is bonded to the inner side of the composite component and compressed in such a manner that its volume is reduced as compared to a pre-assembly state.
By being compressed in a suitable pressing tool, the rigid-foam or semi-rigid-foam plate, which is bonded to the composite component across a large surface or to parts thereof, accommodates irregularities and surface protrusions of the composite component auf, whereas the outer side, i.e. the side of the foam material facing away from the composite component, is smooth and even, thus allowing it to be lined with a headliner, which then forms a class A surface. Thus, no additional headliner element is required.
The roof shell designed according to the invention and comprising the rigid-foam or semi-rigid-foam plate is produced by first producing the composite component in a corresponding molding tool. Subsequently, the rigid-foam or semi-rigid-foam plate is pressed onto the composite component. For bonding it to the composite component, an adhesive system, such as a spray adhesive or the like, can be used. Joining and compression preferably take place in a press.
If required, a pressing tool including component holders can be used. In particular, one tool half of the tool holds the composite component in a form-fitting manner, thus ensuring a homogenous pressure distribution during compression and avoiding damage to the composite component. A second tool half can be of such a geometric design that height differences, recesses and seams are pressed into the rigid-foam or semi-rigid-foam plate during compression. These deformations are preserved after the pressing process in the rigid-foam plate or semi-rigid-foam plate, which is reduced in volume. Accordingly, height differences, recesses and seams of the composite component due to inserts, for example, are pressed into the rigid-foam or semi-rigid-foam plate. Thus, the appearance of the roof shell on the inner side is not compromised by gaps, ripples or other defects in the composite component.
As apparent from the explanations above, the acoustic insulation layer provided by the rigid-foam or semi-rigid-foam plate is preferably bonded to the composite component through a mold-based pressing process. This process can take place at high process stability and thus with little expenditure in terms of quality control. The resulting component, which is composed of the composite component and the compressed rigid-foam or semi-rigid-foam plate, can be easily lined while offering proper acoustic insulation.
Furthermore, the roof shell comprising the compressed rigid-foam or semi-rigid-foam plate is characterized by low production costs because only little investment is required for the pressing tool as compared to foaming molds. Moreover, a rigid-foam or semi-rigid-foam plate exhibits high dimensional stability.
The rigid-foam or semi-rigid-foam plate advantageously consists of an open-pored rigid foam, which enhances the acoustic insulating properties.
Preferably, the rigid-foam or semi-rigid-foam plate has a density between 50 kg/m3 and 150 kg/m3 when in the compressed state.
A polyurethane-ester foam, a polyethylene foam or any other foam material suitable for the respective roof shell can be used as the material for the rigid-foam or semi-rigid-foam plate.
In a specific embodiment, the roof shell according to the invention forms a roof shell of what is known as a retractable hard top (RHT) of a convertible vehicle, the retractable hard top being composed of rigid roof shells. However, the roof shell can also be a panel bow of what is referred to as panel-bow top, which comprises a foldable top cover fabric.
The invention also relates to a method for producing of a roof shell of a motor vehicle. In this method, the following steps are performed:                producing a panel-type composite element in a molding tool;        placing the panel-type composite element in a pressing tool;        placing a rigid-foam or semi-rigid-foam plate in the pressing tool;        compressing the rigid-foam or semi-rigid-foam plate with the composite component so that the volume of the rigid-foam or semi-rigid-foam plate is reduced and the latter forms an acoustic insulation layer of the roof shell.        